With the increasing ability of designers using CAD systems to specify complex surfaces, there is a similar need for machine tools to articulate about all 5 degrees of freedom to render these surfaces in metals.
Currently most machine mills move the spindle along 3 Cartesian axes, with the 2 axes tilt of the spindle not supported. It would be desirable to substitute the usual fixed axis spindle with one able to additionally tilt in 2 axes such as to upgrade 3 axis machines to 5 axes.
Many solutions to this need have been proposed, however all are compromises involving accuracy, stiffness, compactness and complexity.